1. Field of the Invention
The present disclosure relates to fabrication processes comprising application of certain carbon nanomaterial coatings to polymeric films. Products produced by invention processes include actuating materials, such as solid state actuators that can be used as active element(s) in a printable active origami robot.
2. Description of the Related Art
Polymer based actuators were demonstrated as electroactive devices or as shape memory plastics. See, for example, Bar-Cohen, “Electro-active polymers: current capabilities and challenges”, Paper 4695-02, Proceedings of the SPIE Smart Structures and Materials Symposium, EAPAD Conference, San Diego, Calif., Mar. 18-21, 2002; Jung et al., “Electro-active graphene—Nafion actuators”, Carbon 49 (2011) 1279-1289; and Otero et al., “Soft and Wet Conducting Polymers for Artificial Muscles”, Advanced Materials 10(6), (1998), the disclosures of all of which are hereby incorporated by reference. Many electroactive polymers (EAPs) are based on a capacitor design and are not easily fabricated. Most EAPs are used for artificial muscle. The shape memory polymers commonly actuate only once when heated, unless they are forced out of shape again.
Walking robots have been developed. See Ebefors et al., “The 10th Int Conference on Solid-State Sensors and Actuators (Transducers '99)”, Sendai, Japan, Jun. 7-10, 1999, pp 1202-1205.
Electrostrictive structures including a polymer matrix and carbon nanotubes are described in U.S. Pat. No. 8,076,829 and U.S. Patent Application Publication Nos. 2010/0213790, 2011/0012476, 2011/0094217, and 2011/0234053.
Origami-inspired devices are attractive because a single sheet can be folded into the desired shape, rather than trying to individually fabricate and attach together different components. With the help of geometric folding algorithms and computational tools to determine the folding patterns (see, Demaine et al. in Combinatorial and Computational Geometry, J. P. Jacob E. Goodman, Emo Ed. (2005), vol. 52, pp. 167-211; and Demaine et al. Geometric Folding Algorithms: Linkages Origami Polyhedra. (Cambridge University Press, 2007), pp. 472.), complex 3-D structures can be realized from 2-D forms (see, Stellman et al. Dynamics of Nanostructured Origami. Journal of Microelectromechanical Systems 16, 932 (2007) and Piqué et al. in Laser-based Micro-and Nanopackaging and Assembly VI. (Proc. SPIE 8244, San Francisco, Calif., USA, 2012), pp. 8244), essentially allowing for robots with any form, dimension, and feature to be designed. However, in order to make functional robots, or “active origami”, actuation must be engineered into the origami structures.
Of the many different strategies for actuation, the thermal bimorph actuator is attractive. Actuators that operate on electrochemical double-layer capacitance (see, Baughman et al., Carbon nanotube actuators. Science 284, 1340 (1999); and Landi et al., Single Wall Carbon Nanotube Nafion Composite Actuators. Nano Lett. 2, 1329 (2002)) require an electrolyte, including ionic electroactive polymers (EAPs) (see, Y. Bar-Cohen, in EAPAD Conference. Proceedings of the SPIE Smart Structures and Materials Symposium San Diego, Calif., USA, 2002), vol. Paper 4695-02; and Y. Bar-Cohen, Polymer (EAP) Actuators as Artificial Muscles: Reality, Potential, and Challenges. (SPIE Publications, 2004), vol. PM136, pp. 765) and molecular switches (see, Liu et al., Linear artificial molecular muscles. J. Am. Chem. Soc. 127, 9745 (2005); and, B. K. Juluri et al., A Mechanical Actuator Driven Electrochemically by Artificial Molecular Muscles. Acs Nano 3, 291 (2009); and Pelrine et al., High-speed electrically actuated elastomers with strain greater than 100%. Science 287, 836 (2000)). Dielectric elastomers and piezoelectric actuators (see, Karpelson et al., Driving high voltage piezoelectric actuators in microrobotic applications. Sensor Actuat. a-Phys. 176, 78 (2012)) need high electric fields and voltages. Pneumatically-driven soft robots (see, Shepherd et al., Multigait Soft Robot. Proc. Natl. Acad. Sci. U.S.A. 108 20400 (2011)) require the use of compressed gas. A thermal bimorph actuator exploits the differences in thermal expansion coefficients between two materials, as shown in the classical example of a bimetal thermostat (see, Timoshenko, Analysis of bi-metal thermostats. J. Opt. Soc. Am. Rev. Sci. 11, 233 (1925)). Such electrothermally driven actuation has been demonstrated in microelectromechanical systems (MEMS) (see, Riethmuller et al., Thermally Excited Silicon Microactuators IEEE Trans. Electron Devices 35, 758 (1988)), carbon nanotube/polymer composites (see, Sellinger et al. Electrothermal Polymer Nanocomposite Actuators. Adv. Mater. 22, 3430 (2010); and Hu et al., Electromechanical Actuation with Controllable Motion Based on a Single Walled Carbon Nanotube and Natural Biopolymer Composite. Acs Nano 4, 3498 (2010); and Chen et al., High-Performance, Low-Voltage, and Easy-Operable Bending Actuator Based on Aligned Carbon Nanotube/Polymer Composites. Acs Nano 5, 1588 (2011)), self-folding sheets (see, Hawkes et al., Programmable matter by folding. Proc. Natl. Acad. Sci. U.S.A. 107, 12441 (2010); and Paik et al., in ICMC. (Venice, Italy, 2011)) and has recently been used to impart mobility (e.g. crawling) in a simple worm-like robot through the use of NiTi shape memory springs (see, Cagdas et al. in IEEE (ICRA). (Shanghai, China, 2011)).
However, there is still a need for methods to integrate the actuator with the origami from a cost and fabrication perspective. Also, there is a need for methods that can make it easier to produce different robot designs to suit each particular need.